Conventionally, an opening section that allows a fluid to flow into a container or the like by a self-weight is formed in a vertical wall in terms of satisfactorily releasing air, and is partitioned by a reticular texture such as a net with fine meshes so as to prevent any other things than the fluid, such as dust, from entering the opening section (for example, see PATENT LITERATURE 1).
Furthermore, a structure has been known in which a horizontal wall is connected directly under the opening section which is formed on the vertical wall and is partitioned by the reticular texture (for example, see PATENT LITERATURE 2).